U.S. patent number 7,947,884 [Application Number 12/430,862] was granted by the patent office on 2011-05-24 for plants and seeds of hybrid corn variety ch244084.
This patent grant is currently assigned to Monsanto Technology LLC. Invention is credited to Jeffrey L. McElroy.
United States Patent |
7,947,884 |
McElroy |
May 24, 2011 |
Plants and seeds of hybrid corn variety CH244084
Abstract
According to the invention, there is provided seed and plants of
the hybrid corn variety designated CH244084. The invention thus
relates to the plants, seeds and tissue cultures of the variety
CH244084, and to methods for producing a corn plant produced by
crossing a corn plant of variety CH244084 with itself or with
another corn plant, such as a plant of another variety. The
invention further relates to genetic complements of plants of
variety CH244084.
Inventors: |
McElroy; Jeffrey L. (Mahomet,
IL) |
Assignee: |
Monsanto Technology LLC (St.
Louis, MO)
|
Family
ID: |
42993309 |
Appl.
No.: |
12/430,862 |
Filed: |
April 27, 2009 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20100275302 A1 |
Oct 28, 2010 |
|
Current U.S.
Class: |
800/320.1;
800/302; 800/275; 800/266; 435/412; 800/303; 800/300.1;
800/298 |
Current CPC
Class: |
A01H
5/10 (20130101); A01H 6/4684 (20180501) |
Current International
Class: |
A01H
1/00 (20060101); A01H 5/00 (20060101); A01H
4/00 (20060101); C12N 15/82 (20060101); A01H
5/10 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
US. Appl. No. 12/114,723, filed May 2, 2008, McElroy. cited by
other .
Armstrong et al., "Establishment and maintenance of friable
embryogenic maize callus and the involvement of L-proline," Planta,
164:207-214, 1985. cited by other .
Duvick, "Genetic Contributions to Yield Gains of U.S. Hybrid Maize,
1930 to 1980," Genetic Contributions to Yield Gains of Five Major
Crop Plants: Proceedings of a Symposium sponsored by Div. C-1, Crop
Science Society of America, Dec. 2, 1981 in Atlanta, Georgia; W.R.
Fehr, Crop Science Society of America and American Society of
Agronomy, Madison, Wisconsin, pp. 15-47, 1984. cited by other .
Eshed et al., "Less-than-additive epistatic interactions of
quantitative trait loci in tomato," Genetic, 143:1807-1817, 1996.
cited by other .
Falkner et al., "Lax leaf maize: cell wall composition and
nutritional value," J. Sci. Food Agric., 80:255-262, 2000. cited by
other .
Fehr (ed.), In: Principles of Cultivar Development, vol. 1: Theory
and Technique, pp. 360-376, 1987. cited by other .
Hallauer et al., "Corn breeding," In: Corn and Corn Improvement,
Sprague et al. (Eds.), Madison, Wisconsin, Ch. 8, pp. 463-564,
1988. cited by other .
Kraft et al., "Linkage disequilibrium and fingerprinting in sugar
beet," Theor Appl Genet, 101:323-326, 2000. cited by other .
Krakowsky et al., "Quantitative trait loci for cell wall components
in recombinant inbred lines of maize (zea mays L.) II: leaf sheath
tissue," Theor Appl Genet 112:717-726, 2006. cited by other .
Larson et al., "Corn Production," In: Corn and Corn Improvement,
G.F. Sprague (Ed.), No. 18 in Agronomy Series, American Society of
Agronomy, Inc., Madison, Wisconsin, pp. 625-669, 1977. cited by
other .
Meghji et al., "Inbreeding depression, inbred and hybrid grain
yields, and other traits of maize genotypes representing three
eras," Crop Science, 24:545-549, 1984. cited by other .
Poehlman et al. (eds), Breeding Field Crops, 4th Ed., pp. 172-175,
1995. cited by other .
Poehlman, Breeding Field Crops, 3rd ed., AVI Publishing Company,
Westport, Connecticut, pp. 469-481, 1987. cited by other .
Rieger et al., Glossary of Genetics and Cytogenetics, Classical and
Molecular, Springer-Verlag, Berlin, p. 116, 1976. cited by other
.
Sprague et al., "Corn Breeding," In: Corn and Corn Improvements,
G.F. Sprague (Ed.), No. 18 in Agronomy Series, American Society of
Agronomy, Inc., Madison, Wisconsin, pp. 305-362, 1977. cited by
other .
Troyer, "A retrospective view of corn genetic resources," Journal
of Heredity, 81:17-24, 1990. cited by other .
Wych, "Production of hybrid seed corn," In: Corn and Corn
Improvement, Sprague et al. (Eds.), Madison, Wisconsin, Ch. 9, pp.
565-607, 1988. cited by other.
|
Primary Examiner: Kruse; David H
Attorney, Agent or Firm: SNR Denton US LLP
Claims
What is claimed is:
1. A seed of the hybrid corn variety CH244084, produced by crossing
a first plant of variety CV721680 with a second plant of variety
I226218, wherein representative seed of said varieties CV721680 and
I226218 have been deposited under ATCC Accession numbers PTA-10048
and PTA-7973, respectively.
2. A plant of the hybrid corn variety CH244084 grown from the seed
of claim 1.
3. A plant part of the plant of claim 2.
4. The plant part of claim 3, further defined as an ear, ovule,
pollen or cell.
5. A tissue culture of cells of the plant of claim 2.
6. The tissue culture of claim 5, wherein cells of the tissue
culture are from a tissue selected from the group consisting of
leaf, pollen, embryo, root, root tip, anther, silk, flower, kernel,
ear, cob, husk, stalk and meristem.
7. A seed of the hybrid corn variety CH244084, produced by crossing
a first plant of variety CV721680 with a second plant of variety
I226218, wherein representative seed of said varieties CV721680 and
I226218 have been deposited under ATCC Accession numbers PTA-10048
and PTA-7973, respectively, wherein one or both of the first and
second plants further comprises a transgene that is inherited by
the seed.
8. The seed of claim 7, wherein the transgene confers a trait
selected from the group consisting of male sterility, herbicide
tolerance, insect resistance, disease resistance, waxy starch,
modified fatty acid metabolism, modified phytic acid metabolism,
modified carbohydrate metabolism and modified protein
metabolism.
9. The seed of claim 7, wherein the first and second plants each
comprise a different transgene.
10. A seed of the hybrid corn variety CH244084, produced by
crossing a first plant of variety CV721680 with a second plant of
variety I226218, wherein representative seed of said varieties
CV721680 and I226218 have been deposited under ATCC Accession
numbers PTA-10048 and PTA-7973, respectively, wherein one or both
of the first and second plants comprises a single locus conversion
that is inherited by the seed.
11. The seed of claim 10, wherein the single locus conversion
confers a trait selected from the group consisting of male
sterility, herbicide tolerance, insect resistance, disease
resistance, waxy starch, modified fatty acid metabolism, modified
phytic acid metabolism, modified carbohydrate metabolism and
modified protein metabolism.
12. A method of producing hybrid corn seed comprising crossing a
plant of variety CV721680 with a plant of variety I226218, wherein
representative seed of variety CV721680 and variety I226218 have
been deposited under ATCC Accession numbers PTA-10048 and PTA-7973,
respectively.
13. The method of claim 12, defined as comprising pollinating a
plant of inbred variety CV721680 with pollen from a plant of
variety I226218.
14. The method of claim 12, defined as comprising pollinating a
plant of inbred variety I226218 with pollen from a plant of variety
CV721680.
15. A method for producing corn grain comprising growing the plant
of claim 2 until grain is produced and collecting the grain.
16. A method of introducing a heritable trait into hybrid corn
variety CH244084 comprising the steps of: (a) crossing a first
plant of a first inbred corn variety selected from the group
consisting of variety CV721680 and variety I226218 with another
corn plant that heritably carries the trait to produce progeny
plants, at least some of which heritably carry the trait, wherein
representative samples of seed of variety CV721680 and variety
I226218 have been deposited under ATCC Accession numbers PTA-10048
and PTA-7973, respectively; (b) selecting progeny plants that
heritably carry the trait; (c) crossing selected progeny plants
with another plant of the first inbred corn variety to produce
next-generation progeny plants at least some of which heritably
carry the trait; (d) selecting next-generation progeny plants that
heritably carry the trait and exhibit morphological and
physiological characteristics of the first inbred corn variety; (e)
repeating steps (c) and (d) three or more times to produce at least
a first selected progeny plant that heritably carries the trait and
exhibits essentially all of the morphological and physical
characteristics of the inbred corn variety; and (f) crossing a
progeny plant of step (e) with a plant of the other inbred corn
variety of the group consisting of CV721680 and I226218 to produce
a plant comprising the trait and essentially all of the
characteristics of hybrid corn variety CH244084 when grown under
the same environmental conditions.
17. The method of claim 16, wherein the trait is selected from the
group consisting of male sterility, herbicide tolerance, insect
resistance, disease resistance, waxy starch, modified fatty acid
metabolism, modified phytic acid metabolism, modified carbohydrate
metabolism and modified protein metabolism.
18. The method of claim 17, further comprising repeating steps
(a)-(f) at least once to introduce at least a second trait into
hybrid corn variety CH244084, wherein the second trait is selected
from the group consisting of male sterility, herbicide tolerance,
insect resistance, disease resistance, waxy starch, modified fatty
acid metabolism, modified phytic acid metabolism, modified
carbohydrate metabolism and modified protein metabolism.
19. A plant produced by the method of claim 16.
20. A method of introducing a desired trait into hybrid corn
variety CH244084 comprising the steps of: (a) introducing a
transgene conferring the trait into a variety selected from the
group consisting of CV721680 and I226218 to produce a transgenic
plant heritably carrying the trait, wherein representative samples
of seed of variety CV721680 and variety I226218 have been deposited
under ATCC Accession numbers PTA-10048 and PTA-7973, respectively;
and (b) crossing the transgenic plant or an isogenic progeny plant
thereof with a plant of the other inbred corn variety to produce
seed of the hybrid corn variety CH244084 that heritably carries and
expresses the transgene and otherwise has essentially all of the
morphological and physiological characteristics of hybrid corn
variety CH244084 when grown under the same environmental
conditions.
21. The method of claim 20, wherein the desired trait selected from
the group consisting of male sterility, herbicide tolerance, insect
resistance, disease resistance, waxy starch, modified fatty acid
metabolism, modified phytic acid metabolism, modified carbohydrate
metabolism and modified protein metabolism.
22. The method of claim 20, further comprising repeating steps (a)
and (b) at least once to introduce at least a second trait into
hybrid corn variety CH244084, wherein the second trait is selected
from the group consisting of male sterility, herbicide tolerance,
insect resistance, disease resistance, waxy starch, modified fatty
acid metabolism, modified phytic acid metabolism, modified
carbohydrate metabolism and modified protein metabolism.
23. A plant produced by the method of claim 20.
24. The plant of claim 23, wherein the plant comprises a trait
selected from the group consisting of male sterility, herbicide
tolerance, insect resistance, disease resistance, waxy starch,
modified fatty acid metabolism, modified phytic acid metabolism,
modified carbohydrate metabolism and modified protein
metabolism.
25. A method of producing a corn plant derived from the hybrid corn
variety CH244084, comprising crossing the plant of claim 2 with a
second corn plant to produce a progeny corn plant derived from the
hybrid corn variety CH244084.
26. The method of claim 25, further defined as comprising producing
a corn plant derived from the hybrid corn variety CH244084, the
method comprising the steps of: (a) crossing the progeny corn plant
derived from the hybrid corn variety CH244084 with itself or a
second plant to produce a seed of a progeny plant of a subsequent
generation; (b) growing a progeny plant of a subsequent generation
from the seed and crossing the progeny plant of a subsequent
generation with itself or a second plant; and (c) repeating steps
(a) and (b) for an additional 3-10 generations to produce a corn
plant derived from the hybrid corn variety CH244084.
27. The method of claim 26, further comprising the step of: (d)
crossing the corn plant derived from the hybrid corn variety
CH244084 with a second, distinct corn plant.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of corn
breeding. In particular, the invention relates to corn seed and
plants of the hybrid variety designated CH244084, and derivatives
and tissue cultures thereof.
2. Description of Related Art
The goal of field crop breeding is to combine various desirable
traits in a single variety/hybrid. Such desirable traits include
greater yield, better stalks, better roots, resistance to
insecticides, herbicides, pests, and disease, tolerance to heat and
drought, reduced time to crop maturity, better agronomic quality,
higher nutritional value, and uniformity in germination times,
stand establishment, growth rate, maturity, and fruit size.
Breeding techniques take advantage of a plant's method of
pollination. There are two general methods of pollination: a plant
self-pollinates if pollen from one flower is transferred to the
same or another flower of the same plant. A plant cross-pollinates
if pollen comes to it from a flower on a different plant.
Corn plants (Zea mays L.) can be bred by both self-pollination and
cross-pollination. Both types of pollination involve the corn
plant's flowers. Corn has separate male and female flowers on the
same plant, located on the tassel and the ear, respectively.
Natural pollination occurs in corn when wind blows pollen from the
tassels to the silks that protrude from the tops of the ear
shoot.
Plants that have been self-pollinated and selected for type over
many generations become homozygous at almost all gene loci and
produce a uniform population of true breeding progeny, a homozygous
plant. A cross between two such homozygous plants produces a
uniform population of hybrid plants that are heterozygous for many
gene loci. Conversely, a cross of two plants each heterozygous at a
number of loci produces a population of hybrid plants that differ
genetically and are not uniform. The resulting non-uniformity makes
performance unpredictable.
The development of uniform corn plant hybrids requires the
development of homozygous inbred plants, the crossing of these
inbred plants, and the evaluation of the crosses. Pedigree breeding
and recurrent selection are examples of breeding methods used to
develop hybrid parent plants from breeding populations. Those
breeding methods combine the genetic backgrounds from two or more
inbred plants or various other broad-based sources into breeding
pools from which new inbred plants are developed by selfing and
selection of desired phenotypes. The new inbreds are crossed with
other inbred plants and the hybrids from these crosses are
evaluated to determine which of those have commercial
potential.
North American farmers plant tens of millions of acres of corn at
the present time and there are extensive national and international
commercial corn breeding programs. A continuing goal of these corn
breeding programs is to develop corn hybrids that are based on
stable inbred plants and have one or more desirable
characteristics. To accomplish this goal, the corn breeder must
select and develop superior inbred parental plants.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a corn plant of the
hybrid variety designated CH244084. Also provided are corn plants
having all the physiological and morphological characteristics of
the hybrid corn variety CH244084. A hybrid corn plant of the
invention may further comprise a cytoplasmic or nuclear factor that
is capable of conferring male sterility or otherwise preventing
self-pollination, such as by self-incompatibility. Parts of the
corn plant of the present invention are also provided, for example,
pollen obtained from a hybrid plant and an ovule of the hybrid
plant. The invention also concerns seed of the hybrid corn variety
CH244084. The hybrid corn seed of the invention may be provided as
a population of corn seed of the variety designated CH244084.
In another aspect of the invention, the hybrid corn variety
CH244084 is provided comprising an added desired trait. The desired
trait may be a genetic locus that is a dominant or recessive
allele. In certain embodiments of the invention, the genetic locus
confers traits such as, for example, male sterility, waxy starch,
herbicide resistance, insect resistance, resistance to bacterial,
fungal, nematode or viral disease, and altered fatty acid, phytate
or carbohydrate metabolism. The genetic locus may be a naturally
occurring corn gene introduced into the genome of a parent of the
variety by backcrossing, a natural or induced mutation, or a
transgene introduced through genetic transformation techniques.
When introduced through transformation, a genetic locus may
comprise one or more transgenes integrated at a single chromosomal
location.
In yet another aspect of the invention, a hybrid corn plant of the
variety designated CH244084 is provided, wherein a
cytoplasmically-inherited trait has been introduced into said
hybrid plant. Such cytoplasmically-inherited traits are passed to
progeny through the female parent in a particular cross. An
exemplary cytoplasmically-inherited trait is the male sterility
trait. Cytoplasmic-male sterility (CMS) is a pollen abortion
phenomenon determined by the interaction between the genes in the
cytoplasm and the nucleus. Alteration in the mitochondrial genome
and the lack of restorer genes in the nucleus will lead to pollen
abortion. With either a normal cytoplasm or the presence of
restorer gene(s) in the nucleus, the plant will produce pollen
normally. A CMS plant can be pollinated by a maintainer version of
the same variety, which has a normal cytoplasm but lacks the
restorer gene(s) in the nucleus, and continue to be male sterile in
the next generation. The male fertility of a CMS plant can be
restored by a restorer version of the same variety, which must have
the restorer gene(s) in the nucleus. With the restorer gene(s) in
the nucleus, the offspring of the male-sterile plant can produce
normal pollen grains and propagate. A cytoplasmically inherited
trait may be a naturally occurring maize trait or a trait
introduced through genetic transformation techniques.
In another aspect of the invention, a tissue culture of regenerable
cells of a plant of variety CH244084 is provided. The tissue
culture will preferably be capable of regenerating plants capable
of expressing all of the physiological and morphological
characteristics of the variety, and of regenerating plants having
substantially the same genotype as other plants of the variety.
Examples of some of the physiological and morphological
characteristics of the variety CH244084 include characteristics
related to yield, maturity, and kernel quality, each of which is
specifically disclosed herein. The regenerable cells in such tissue
cultures will preferably be derived from embryos, meristematic
cells, immature tassels, microspores, pollen, leaves, anthers,
roots, root tips, silk, flowers, kernels, ears, cobs, husks, or
stalks, or from callus or protoplasts derived from those tissues.
Still further, the present invention provides corn plants
regenerated from the tissue cultures of the invention, the plants
having all the physiological and morphological characteristics of
variety CH244084.
In still another aspect, the invention provides a method of
producing hybrid corn seed comprising crossing a plant of variety
CV721680 with a plant of variety I226218. In a cross, either parent
may serve as the male or female. Processes are also provided for
producing corn seeds or plants, which processes generally comprise
crossing a first parent corn plant with a second parent corn plant,
wherein at least one of the first or second parent corn plants is a
plant of the variety designated CH244084. In such crossing, either
parent may serve as the male or female parent. These processes may
be further exemplified as processes for preparing hybrid corn seed
or plants, wherein a first hybrid corn plant is crossed with a
second corn plant of a different, distinct variety to provide a
hybrid that has, as one of its parents, the hybrid corn plant
variety CH244084. In these processes, crossing will result in the
production of seed. The seed production occurs regardless of
whether the seed is collected or not.
In one embodiment of the invention, the first step in "crossing"
comprises planting, preferably in pollinating proximity, seeds of a
first and second parent corn plant, and preferably, seeds of a
first corn plant and a second, distinct corn plant. Where the
plants are not in pollinating proximity, pollination can
nevertheless be accomplished by transferring a pollen or tassel bag
from one plant to the other as described below.
A second step comprises cultivating or growing the seeds of said
first and second parent corn plants into plants that bear flowers
(corn bears both male flowers (tassels) and female flowers (silks)
in separate anatomical structures on the same plant). A third step
comprises preventing self-pollination of the plants, i.e.,
preventing the silks of a plant from being fertilized by any plant
of the same variety, including the same plant. This is preferably
done by emasculating the male flowers of the first or second parent
corn plant, (i.e., treating or manipulating the flowers so as to
prevent pollen production, in order to produce an emasculated
parent corn plant). Self-incompatibility systems may also be used
in some hybrid crops for the same purpose. Self-incompatible plants
still shed viable pollen and can pollinate plants of other
varieties but are incapable of pollinating themselves or other
plants of the same variety.
A fourth step may comprise allowing cross-pollination to occur
between the first and second parent corn plants. When the plants
are not in pollinating proximity, this is done by placing a bag,
usually paper or glassine, over the tassels of the first plant and
another bag over the silks of the incipient ear on the second
plant. The bags are left in place for at least 24 hours. Since
pollen is viable for less than 24 hours, this assures that the
silks are not pollinated from other pollen sources, that any stray
pollen on the tassels of the first plant is dead, and that the only
pollen transferred comes from the first plant. The pollen bag over
the tassel of the first plant is then shaken vigorously to enhance
release of pollen from the tassels, and the shoot bag is removed
from the silks of the incipient ear on the second plant. Finally,
the pollen bag is removed from the tassel of the first plant and is
placed over the silks of the incipient ear of the second plant,
shaken again and left in place. Yet another step comprises
harvesting the seeds from at least one of the parent corn plants.
The harvested seed can be grown to produce a corn plant or hybrid
corn plant.
The present invention also provides corn seed and plants produced
by a process that comprises crossing a first parent corn plant with
a second parent corn plant, wherein at least one of the first or
second parent corn plants is a plant of the variety designated
CH244084. In one embodiment of the invention, corn seed and plants
produced by the process are first generation hybrid corn seed and
plants produced by crossing an inbred with another, distinct
inbred. The present invention further contemplates seed of an
F.sub.1 hybrid corn plant. Therefore, certain exemplary embodiments
of the invention provide an F.sub.1 hybrid corn plant and seed
thereof, specifically the hybrid variety designated CH244084.
Such a plant can be analyzed by its "genetic complement." This term
is used to refer to the aggregate of nucleotide sequences, the
expression of which defines the phenotype of, for example, a corn
plant, or a cell or tissue of that plant. A genetic complement thus
represents the genetic make up of an cell, tissue or plant. The
invention thus provides corn plant cells that have a genetic
complement in accordance with the corn plant cells disclosed
herein, and plants, seeds and diploid plants containing such
cells.
Plant genetic complements may be assessed by genetic marker
profiles, and by the expression of phenotypic traits that are
characteristic of the expression of the genetic complement, e.g.,
marker typing profiles. It is known in the art that such
complements may also be identified by marker types including, but
not limited to, SSRs, Simple Sequence Length Polymorphisms (SSLPs)
(Williams et al., 1990), Randomly Amplified Polymorphic DNAs
(RAPDs), DNA Amplification Fingerprinting (DAF), Sequence
Characterized Amplified Regions (SCARs), Arbitrary Primed
Polymerase Chain Reaction (AP-PCR), Amplified Fragment Length
Polymorphisms (AFLPs) (EP 534 858, specifically incorporated herein
by reference in its entirety), and Single Nucleotide Polymorphisms
(SNPs) (Wang et al., 1998).
DETAILED DESCRIPTION OF THE INVENTION
I. Definitions of Plant Characteristics
Barren Plants: Plants that are barren, i.e., lack an ear with
grain, or have an ear with only a few scattered kernels.
Cg: Colletotrichum graminicola rating. Rating times 10 is
approximately equal to percent total plant infection.
CLN: Corn Lethal Necrosis (combination of Maize Chlorotic Mottle
Virus and Maize Dwarf Mosaic virus) rating: numerical ratings are
based on a severity scale where 1=most resistant to
9=susceptible.
Cn: Corynebacterium nebraskense rating. Rating times 10 is
approximately equal to percent total plant infection.
Cz: Cercospora zeae-maydis rating. Rating times 10 is approximately
equal to percent total plant infection.
Dgg: Diatraea grandiosella girdling rating (values are percent
plants girdled and stalk lodged).
Dropped Ears: Ears that have fallen from the plant to the
ground.
Dsp: Diabrotica species root ratings (1=least affected to 9=severe
pruning).
Ear-Attitude: The attitude or position of the ear at harvest scored
as upright, horizontal, or pendant.
Ear-Cob Color: The color of the cob, scored as white, pink, red, or
brown.
Ear-Cob Diameter: The average diameter of the cob measured at the
midpoint.
Ear-Cob Strength: A measure of mechanical strength of the cobs to
breakage, scored as strong or weak.
Ear-Diameter: The average diameter of the ear at its midpoint.
Ear-Dry Husk Color: The color of the husks at harvest scored as
buff, red, or purple.
Ear-Fresh Husk Color: The color of the husks 1 to 2 weeks after
pollination scored as green, red, or purple.
Ear-Husk Bract: The length of an average husk leaf scored as short,
medium, or long.
Ear-Husk Cover: The average distance from the tip of the ear to the
tip of the husks. Minimum value no less than zero.
Ear-Husk Opening: An evaluation of husk tightness at harvest scored
as tight, intermediate, or open.
Ear-Length: The average length of the ear.
Ear-Number Per Stalk: The average number of ears per plant.
Ear-Shank Internodes: The average number of internodes on the ear
shank.
Ear-Shank Length: The average length of the ear shank.
Ear-Shelling Percent: The average of the shelled grain weight
divided by the sum of the shelled grain weight and cob weight for a
single ear.
Ear-Silk Color: The color of the silk observed 2 to 3 days after
silk emergence scored as green-yellow, yellow, pink, red, or
purple.
Ear-Taper (Shape): The taper or shape of the ear scored as conical,
semi-conical, or cylindrical.
Ear-Weight: The average weight of an ear.
Early Stand: The percent of plants that emerge from the ground as
determined in the early spring.
ER: Ear rot rating (values approximate percent ear rotted).
Final Stand Count: The number of plants just prior to harvest.
GDUs: Growing degree units which are calculated by the Barger
Method, where the heat units for a 24-h period are calculated as
GDUs=[(Maximum daily temperature+Minimum daily temperature)/2]-50.
The highest maximum daily temperature used is 86.degree. F. and the
lowest minimum temperature used is 50.degree. F.
GDUs to Shed: The number of growing degree units (GDUs) or heat
units required for a variety to have approximately 50% of the
plants shedding pollen as measured from time of planting. GDUs to
shed is determined by summing the individual GDU daily values from
planting date to the date of 50% pollen shed.
GDUs to Silk: The number of growing degree units for a variety to
have approximately 50% of the plants with silk emergence as
measured from time of planting. GDUs to silk is determined by
summing the individual GDU daily values from planting date to the
date of 50% silking.
Hc2: Helminthosporium carbonum race 2 rating. Rating times 10 is
approximately equal to percent total plant infection.
Hc3: Helminthosporium carbonum race 3 rating. Rating times 10 is
approximately equal to percent total plant infection.
Hm: Helminthosporium maydis race 0 rating. Rating times 10 is
approximately equal to percent total plant infection.
Ht1: Helminthosporium turcicum race 1 rating. Rating times 10 is
approximately equal to percent total plant infection.
Ht2: Helminthosporium turcicum race 2 rating. Rating times 10 is
approximately equal to percent total plant infection.
HtG: Chlorotic-lesion type resistance. +=indicates the presence of
Ht chlorotic-lesion type resistance; -=indicates absence of Ht
chlorotic-lesion type resistance; and +/-=indicates segregation of
Ht chlorotic-lesion type resistance. Rating times 10 is
approximately equal to percent total plant infection.
Kernel-Aleurone Color: The color of the aleurone scored as white,
pink, tan, brown, bronze, red, purple, pale purple, colorless, or
variegated.
Kernel-Cap Color: The color of the kernel cap observed at dry
stage, scored as white, lemon-yellow, yellow, or orange.
Kernel-Endosperm Color: The color of the endosperm scored as white,
pale yellow, or yellow.
Kernel-Endosperm Type: The type of endosperm scored as normal,
waxy, or opaque.
Kernel-Grade: The percent of kernels that are classified as
rounds.
Kernel-Length: The average distance from the cap of the kernel to
the pedicel.
Kernel-Number Per Row: The average number of kernels in a single
row.
Kernel-Pericarp Color: The color of the pericarp scored as
colorless, red-white crown, tan, bronze, brown, light red, cherry
red, or variegated.
Kernel-Row Direction: The direction of the kernel rows on the ear
scored as straight, slightly curved, spiral, or indistinct
(scattered).
Kernel-Row Number: The average number of rows of kernels on a
single ear.
Kernel-Side Color: The color of the kernel side observed at the dry
stage, scored as white, pale yellow, yellow, orange, red, or
brown.
Kernel-Thickness: The distance across the narrow side of the
kernel.
Kernel-Type: The type of kernel scored as dent, flint, or
intermediate.
Kernel-Weight: The average weight of a predetermined number of
kernels.
Kernel-Width: The distance across the flat side of the kernel.
Kz: Kabatiella zeae rating. Rating times 10 is approximately equal
to percent total plant infection.
Leaf-Angle: Angle of the upper leaves to the stalk scored as
upright (0 to 30 degrees), intermediate (30 to 60 degrees), or lax
(60 to 90 degrees).
Leaf-Color: The color of the leaves 1 to 2 weeks after pollination
scored as light green, medium green, dark green, or very dark
green.
Leaf-Length: The average length of the primary ear leaf.
Leaf-Longitudinal Creases: A rating of the number of longitudinal
creases on the leaf surface 1 to 2 weeks after pollination. Creases
are scored as absent, few, or many.
Leaf-Marginal Waves: A rating of the waviness of the leaf margin 1
to 2 weeks after pollination. Rated as none, few, or many.
Leaf-Number: The average number of leaves of a mature plant.
Counting begins with the cotyledonary leaf and ends with the flag
leaf.
Leaf-Sheath Anthocyanin: A rating of the level of anthocyanin in
the leaf sheath 1 to 2 weeks after pollination, scored as absent,
basal-weak, basal-strong, weak or strong.
Leaf-Sheath Pubescence: A rating of the pubescence of the leaf
sheath. Ratings are taken 1 to 2 weeks after pollination and scored
as light, medium, or heavy.
Leaf-Width: The average width of the primary ear leaf measured at
its widest point.
LSS: Late season standability (values times 10 approximate percent
plants lodged in disease evaluation plots).
Moisture: The moisture of the grain at harvest.
On1: Ostrinia nubilalis 1st brood rating (1=resistant to
9=susceptible).
On2: Ostrinia nubilalis 2nd brood rating (1=resistant to
9=susceptible).
Relative Maturity: A maturity rating based on regression analysis.
The regression analysis is developed by utilizing check hybrids and
their previously established day rating versus actual harvest
moistures. Harvest moisture on the hybrid in question is determined
and that moisture value is inserted into the regression equation to
yield a relative maturity.
Root Lodging: Root lodging is the percentage of plants that root
lodge. A plant is counted as root lodged if a portion of the plant
leans from the vertical axis by approximately 30 degrees or
more.
Seedling Color: Color of leaves at the 6 to 8 leaf stage.
Seedling Height: Plant height at the 6 to 8 leaf stage.
Seedling Vigor: A visual rating of the amount of vegetative growth
on a 1 to 9 scale, where 1 equals best. The score is taken when the
average entry in a trial is at the fifth leaf stage.
Selection Index: The selection index gives a single measure of
hybrid's worth based on information from multiple traits. One of
the traits that is almost always included is yield. Traits may be
weighted according to the level of importance assigned to them.
Sr: Sphacelotheca reiliana rating is actual percent infection.
Stalk-Anthocyanin: A rating of the amount of anthocyanin
pigmentation in the stalk. The stalk is rated 1 to 2 weeks after
pollination as absent, basal-weak, basal-strong, weak, or
strong.
Stalk-Brace Root Color: The color of the brace roots observed 1 to
2 weeks after pollination as green, red, or purple.
Stalk-Diameter: The average diameter of the lowest visible
internode of the stalk.
Stalk-Ear Height: The average height of the ear measured from the
ground to the point of attachment of the ear shank of the top
developed ear to the stalk.
Stalk-Internode Direction: The direction of the stalk internode
observed after pollination as straight or zigzag.
Stalk-Internode Length: The average length of the internode above
the primary ear.
Stalk Lodging: The percentage of plants that did stalk lodge.
Plants are counted as stalk lodged if the plant is broken over or
off below the ear.
Stalk-Nodes With Brace Roots: The average number of nodes having
brace roots per plant.
Stalk-Plant Height: The average height of the plant as measured
from the soil to the tip of the tassel.
Stalk-Tillers: The percent of plants that have tillers. A tiller is
defined as a secondary shoot that has developed as a tassel capable
of shedding pollen.
Staygreen: Staygreen is a measure of general plant health near the
time of black layer formation (physiological maturity). It is
usually recorded at the time the ear husks of most entries within a
trial have turned a mature color. Scoring is on a 1 to 9 basis
where 1 equals best.
STR: Stalk rot rating (values represent severity rating of 1=25% of
inoculated internode rotted to 9=entire stalk rotted and
collapsed).
SVC: Southeastern Virus Complex (combination of Maize Chlorotic
Dwarf Virus and Maize Dwarf Mosaic Virus) rating; numerical ratings
are based on a severity scale where 1=most resistant to
9=susceptible (1988 reactions are largely Maize Dwarf Mosaic Virus
reactions).
Tassel-Anther Color: The color of the anthers at 50% pollen shed
scored as green-yellow, yellow, pink, red, or purple.
Tassel-Attitude: The attitude of the tassel after pollination
scored as open or compact.
Tassel-Branch Angle: The angle of an average tassel branch to the
main stem of the tassel scored as upright (less than 30 degrees),
intermediate (30 to 45 degrees), or lax (greater than 45
degrees).
Tassel-Branch Number: The average number of primary tassel
branches.
Tassel-Glume Band: The closed anthocyanin band at the base of the
glume scored as present or absent.
Tassel-Glume Color: The color of the glumes at 50% shed scored as
green, red, or purple.
Tassel-Length: The length of the tassel measured from the base of
the bottom tassel branch to the tassel tip.
Tassel-Peduncle Length: The average length of the tassel peduncle,
measured from the base of the flag leaf to the base of the bottom
tassel branch.
Tassel-Pollen Shed: A visual rating of pollen shed determined by
tapping the tassel and observing the pollen flow of approximately
five plants per entry. Rated on a 1 to 9 scale where 9=sterile,
1=most pollen.
Tassel-Spike Length: The length of the spike measured from the base
of the top tassel branch to the tassel tip.
Test Weight: Weight of the grain in pounds for a given volume
(bushel) adjusted to 15.5% moisture.
Yield: Yield of grain at harvest adjusted to 15.5% moisture.
II. Other Definitions
Allele: Any of one or more alternative forms of a gene locus, all
of which alleles relate to one trait or characteristic. In a
diploid cell or organism, the two alleles of a given gene occupy
corresponding loci on a pair of homologous chromosomes.
Backcrossing: A process in which a breeder repeatedly crosses
hybrid progeny back to one of the parents, for example, a first
generation hybrid (F.sub.1) with one of the parental genotypes of
the F.sub.1 hybrid.
Crossing: The pollination of a female flower of a corn plant,
thereby resulting in the production of seed from the flower.
Cross-pollination: Fertilization by the union of two gametes from
different plants.
Diploid: A cell or organism having two sets of chromosomes.
Emasculate: The removal of plant male sex organs or the
inactivation of the organs with a chemical agent or a cytoplasmic
or nuclear genetic factor conferring male sterility.
F.sub.1 Hybrid: The first generation progeny of the cross of two
plants.
Genetic Complement: An aggregate of nucleotide sequences, the
expression of which sequences defines the phenotype in corn plants,
or components of plants including cells or tissue.
Genotype: The genetic constitution of a cell or organism.
Haploid: A cell or organism having one set of the two sets of
chromosomes in a diploid.
Marker: A readily detectable phenotype, preferably inherited in
codominant fashion (both alleles at a locus in a diploid
heterozygote are readily detectable), with no environmental
variance component, i.e., heritability of 1.
Phenotype: The detectable characteristics of a cell or organism,
which characteristics are the manifestation of gene expression.
Quantitative Trait Loci (QTL): Genetic loci that contribute, at
least in part, certain numerically representable traits that are
usually continuously distributed.
Regeneration: The development of a plant from tissue culture.
Self-pollination: The transfer of pollen from the anther to the
stigma of the same plant.
Single Locus Converted (Conversion) Plant: Plants which are
developed by a plant breeding technique called backcrossing wherein
essentially all of the desired morphological and physiological
characteristics of an inbred are recovered in addition to the
characteristics conferred by the single locus transferred into the
inbred via the backcrossing technique. A single locus may comprise
one gene, or in the case of transgenic plants, one or more
transgenes integrated into the host genome at a single site
(locus).
Tissue Culture: A composition comprising isolated cells of the same
or a different type or a collection of such cells organized into
parts of a plant.
Transgene: A genetic sequence which has been introduced into the
nuclear or chloroplast genome of a corn plant by a genetic
transformation technique.
III. Variety Descriptions
In accordance with one aspect of the present invention, there is
provided a novel hybrid corn plant variety designated CH244084.
Hybrid variety CH244084 was produced from a cross of the inbred
varieties designated CV721680 and I226218. The inbred parents have
been self-pollinated and ear-rowed a sufficient number of
generations with careful attention paid to uniformity of plant type
to show uniformity and stability within the limits of environmental
influence.
In accordance with one aspect of the invention, there is provided a
corn plant having the physiological and morphological
characteristics of corn plant CH244084. An analysis of such
morphological traits was carried out, the results of which are
presented in Table 1.
TABLE-US-00001 TABLE 1 Morphological Traits for Hybrid Variety
CH244084 CHARACTERISTIC VALUE 1. STALK Plant Height cm. 278.7 Ear
Height cm. 96.7 Anthocyanin Absent Brace Root Color Faint Internode
Direction Straight Internode Length cm. 18.8 2. LEAF Color Dark
Green Length cm. 92.5 Width cm. 10.3 Sheath Anthocyanin Absent
Sheath Pubescence Medium Marginal Waves Moderate Longitudinal
Creases Moderate 3. TASSEL Length cm. 49.0 Peduncle Length cm. 10.4
Branch Number 6.0 Anther Color Salmon Glume Color Pale Purple Glume
Band Absent 4. EAR Silk Color Green-Yellow Number Per Stalk 1.0
Length cm. 17.2 Diameter cm. 4.8 Shank Length cm. 9.7 Husk Bract
Short Husk Cover cm. 3.5 Husk Color Fresh Green Husk Color Dry Buff
Cob Diameter cm. 2.6 Shelling Percent 90.1 5. KERNEL Row Number
17.0 Number Per Row 34.0 Type Dent Length (depth) mm. 13.0 Width
mm. 7.1 Thickness 4.8 Endosperm Type Normal Endosperm Color Yellow
*These are typical values. Values may vary due to environment.
Other values that are substantially equivalent are also within the
scope of the invention.
During the development of a hybrid plant detailed evaluations of
the phenotype are made including formal comparisons with other
commercially successful hybrids. Because the corn is grown in close
proximity, environmental factors that affect gene expression, such
as moisture, temperature, sunlight, and pests, are minimized. For a
decision to be made to commercialize a hybrid, it is not necessary
that the hybrid be better than all other hybrids. Rather,
significant improvements must be shown in at least some traits that
would create improvements in some niches. Examples of such
comparative performance data for the hybrid corn plant CH244084 are
set forth herein below in Table 2.
TABLE-US-00002 TABLE 2 Comparison of CH244084 With a Selected
Hybrid Variety SI YLD MST STL RTL DRP FLSTD SV PHT EHT SG TST
HYBRID % C BU PTS % % % % M RAT INCH INCH RAT LBS CH244084 108.2
216.2 10.6 4.3 1.4 0.0 160.8 4.8 96.9 42.5 5.9 57.1 DKC60-17 100.4
209.7 10.1 2.9 3.4 0.0 162.8 4.1 88.4 36.3 7.1 56.7 Diff. 7.9 6.5
0.5 1.4 -2.0 0.0 -2.0 0.7 8.5 6.2 -1.2 0.3 Sign. ** ** ** * * ** **
** ** ** * Significance levels are indicated as: += 10%, * = 5%, **
= 1% LEGEND ABBREVIATIONS: HYBD = Hybrid NTEST = Research/FACT SI %
C = Selection Index (percent of check) YLD BU/A = Yield
(bushels/acre) MST PTS = Moisture STL % = Stalk Lodging (percent)
RTL % = Root Lodging (percent) DRP % = Dropped Ears (percent) FLSTD
% M = Final Stand (percent of test mean) SV RAT = Seedling Vigor
Rating ELSTD % M = Early Stand (percent of test mean) PHT INCH =
Plant Height (inches) EHT INCH = Ear Height (inches) BAR % = Barren
Plants (percent) SG RAT = Staygreen Rating TST LBS = Test Weight
(pounds) FGDU = GDUs to Shed ESTR DAYS = Estimated Relative
Maturity (days)
In accordance with another aspect of the present invention, there
is provided a corn plant having the physiological and morphological
characteristics of corn plant CV721680. A description of the
physiological and morphological characteristics of corn plant
CV721680 is presented in Table 3.
TABLE-US-00003 TABLE 3 Morphological Traits for Corn Variety
CV721680 CHARACTERISTIC CV721680 1. STALK Plant Height (cm.) 244.2
Ear Height (cm) 85.0 Anthocyanin Basal Weak Brace Root Color Faint
Nodes With Brace Roots 2.1 Internode Direction Straight Internode
Length cm. 15.8 2. LEAF Color Dark Green Length cm. 80.0 Width cm.
8.6 Sheath Anthocyanin Absent Sheath Pubescence Heavy Marginal
Waves Moderate Longitudinal Creases Moderate 3. TASSEL Length cm.
37.0 Spike Length cm. 20.2 Peduncle Length cm. 6.6 Branch Number
5.0 Anther Color Pink Glume Color Light Red Glume Band Absent 4.
EAR Silk Color Yellow Number Per Stalk 1.0 Position (attitude)
Upright Length cm. 14.7 Shape Semi-Conical Diameter cm. 4.1 Shank
Length cm. 9.7 Husk Bract Short Husk Cover cm. 5.1 Husk Opening
Tight Husk Color Fresh Green Husk Color Dry Buff Cob Diameter cm.
2.5 Cob Color Red Shelling Percent 85.9 5. KERNEL Row Number 16.0
Number Per Row 30.4 Row Direction Straight Type Dent Cap Color
Yellow Side Color Yellow-Orange Length (depth) mm. 11.2 Width mm.
8.5 Thickness 4.8 Endosperm Type Normal Endosperm Color Yellow
*These are typical values. Values may vary due to environment.
Other values that are substantially equivalent are also within the
scope of the invention.
IV. Deposit Information
A deposit of at least 2500 seeds of inbred parent plant varieties
CV721680 (U.S. application Ser. No. 12/114,723, filed May 2, 2008,
the entire disclosure of which is incorporated herein by reference)
and I226218 (U.S. Pat. No. 7,351,888, the entire disclosure of
which is incorporated herein by reference) was made with the
American Type Culture Collection (ATCC), 10801 University
Boulevard, Manassas, Va. 20110-2209 USA, and assigned ATCC
Accession Nos. PTA-10048, and PTA-7973, respectively. The seeds
were deposited with the ATCC on May 20, 2009, and Nov. 7, 2006,
respectively. Access to the deposits will be available during the
pendency of the application to the Commissioner of Patents and
Trademarks and persons determined by the Commissioner to be
entitled thereto upon request. The deposits will be maintained in
the ATCC Depository, which is a public depository, for a period of
30 years, or 5 years after the most recent request, or for the
enforceable life of the patent, whichever is longer, and will be
replaced if it becomes nonviable during that period. Applicant does
not waive any infringement of their rights granted under this
patent or under the Plant Variety Protection Act (7 U.S.C. 2321 et
seq.).
V. Further Embodiments of the Invention
In certain further aspects, the invention provides plants modified
to include at least a first desired trait. Such plants may, in one
embodiment, be developed by a plant breeding technique called
backcrossing, wherein essentially all of the morphological and
physiological characteristics of a variety are recovered in
addition to a genetic locus transferred into the hybrid via the
backcrossing technique. By essentially all of the morphological and
physiological characteristics, it is meant that all of the
characteristics of a plant are recovered that are otherwise present
when compared in the same environment, other than an occasional
variant trait that might arise during backcrossing or direct
introduction of a transgene. In one embodiment, such traits may be
determined, for example, relative to the traits listed in Table 1
as determined at the 5% significance level when grown under the
same environmental conditions.
Backcrossing methods can be used with the present invention to
improve or introduce a trait in a hybrid via modification of its
inbred parent(s). The term backcrossing as used herein refers to
the repeated crossing of a hybrid progeny back to one of the
parental corn plants for that hybrid. The parental corn plant which
contributes the locus or loci for the desired trait is termed the
nonrecurrent or donor parent. This terminology refers to the fact
that the nonrecurrent parent is used one time in the backcross
protocol and therefore does not recur.
The parental corn plant to which the locus or loci from the
nonrecurrent parent are transferred is known as the recurrent
parent as it is used for several rounds in the backcrossing
protocol (Poehlman et al., 1995; Fehr, 1987; Sprague and Dudley,
1988). In a typical backcross protocol, the original parent hybrid
of interest (recurrent parent) is crossed to a second variety
(nonrecurrent parent) that carries the genetic locus of interest to
be transferred. The resulting progeny from this cross are then
crossed again to the recurrent parent and the process is repeated
until a corn plant is obtained wherein essentially all of the
desired morphological and physiological characteristics of the
recurrent parent are recovered in the converted plant, in addition
to the transferred locus from the nonrecurrent parent. The
backcross process may be accelerated by the use of genetic markers,
such as SSR, RFLP, SNP or AFLP markers to identify plants with the
greatest genetic complement from the recurrent parent.
The selection of a suitable recurrent parent is an important step
for a successful backcrossing procedure. The goal of a backcross
protocol is to add or substitute one or more new traits in the
original inbred and hybrid progeny therefrom. To accomplish this, a
genetic locus of the recurrent parent is modified or substituted
with the desired locus from the nonrecurrent parent, while
retaining essentially all of the rest of the desired genetic, and
therefore the desired physiological and morphological constitution
of the original plant. The choice of the particular nonrecurrent
parent will depend on the purpose of the backcross; one of the
major purposes is to add some commercially desirable, agronomically
important trait to the plant. The exact backcrossing protocol will
depend on the characteristic or trait being altered to determine an
appropriate testing protocol. Although backcrossing methods are
simplified when the characteristic being transferred is a dominant
allele, a recessive allele may also be transferred. In this
instance it may be necessary to introduce a test of the progeny to
determine if the desired characteristic has been successfully
transferred.
Many traits have been identified that are not regularly selected
for in the development of a new variety but that can be improved by
backcrossing techniques. A genetic locus conferring the traits may
or may not be transgenic. Examples of such traits known to those of
skill in the art include, but are not limited to, male sterility,
waxy starch, herbicide resistance, resistance for bacterial,
fungal, or viral disease, insect resistance, male fertility and
enhanced nutritional quality. These genes are generally inherited
through the nucleus, but may be inherited through the cytoplasm.
Some known exceptions to this are genes for male sterility, some of
which are inherited cytoplasmically, but still act as a single
locus trait.
Direct selection may be applied where a genetic locus acts as a
dominant trait. An example of a dominant trait is the herbicide
resistance trait. For this selection process, the progeny of the
initial cross are sprayed with the herbicide prior to the
backcrossing. The spraying eliminates any plants which do not have
the desired herbicide resistance characteristic, and only those
plants which have the herbicide resistance gene are used in the
subsequent backcross. This process is then repeated for all
additional backcross generations.
Many useful traits are those which are introduced by genetic
transformation techniques. Methods for the genetic transformation
of corn are known to those of skill in the art. For example,
methods which have been described for the genetic transformation of
corn include electroporation (U.S. Pat. No. 5,384,253),
electrotransformation (U.S. Pat. No. 5,371,003), microprojectile
bombardment (U.S. Pat. No. 5,550,318; U.S. Pat. No. 5,736,369, U.S.
Pat. No. 5,538,880; and PCT Publication WO 95/06128),
Agrobacterium-mediated transformation (U.S. Pat. No. 5,591,616 and
E.P. Publication EP672752), direct DNA uptake transformation of
protoplasts (Omirulleh et al., 1993) and silicon carbide
fiber-mediated transformation (U.S. Pat. No. 5,302,532 and U.S.
Pat. No. 5,464,765).
It is understood to those of skill in the art that a transgene need
not be directly transformed into a plant, as techniques for the
production of stably transformed corn plants that pass single loci
to progeny by Mendelian inheritance is well known in the art. Such
loci may therefore be passed from parent plant to progeny plants by
standard plant breeding techniques that are well known in the
art.
A. Male Sterility
Examples of genes conferring male sterility include those disclosed
in U.S. Pat. No. 3,861,709, U.S. Pat. No. 3,710,511, U.S. Pat. No.
4,654,465, U.S. Pat. No. 5,625,132, and U.S. Pat. No. 4,727,219,
each of the disclosures of which are specifically incorporated
herein by reference in their entirety. Male sterility genes can
increase the efficiency with which hybrids are made, in that they
eliminate the need to physically emasculate the corn plant used as
a female in a given cross.
Where one desires to employ male-sterility systems with a corn
plant in accordance with the invention, it may be beneficial to
also utilize one or more male-fertility restorer genes. For
example, where cytoplasmic male sterility (CMS) is used, hybrid
seed production requires three inbred lines: (1) a cytoplasmically
male-sterile line having a CMS cytoplasm; (2) a fertile inbred with
normal cytoplasm, which is isogenic with the CMS line for nuclear
genes ("maintainer line"); and (3) a distinct, fertile inbred with
normal cytoplasm, carrying a fertility restoring gene ("restorer"
line). The CMS line is propagated by pollination with the
maintainer line, with all of the progeny being male sterile, as the
CMS cytoplasm is derived from the female parent. These male sterile
plants can then be efficiently employed as the female parent in
hybrid crosses with the restorer line, without the need for
physical emasculation of the male reproductive parts of the female
parent.
The presence of a male-fertility restorer gene results in the
production of fully fertile F.sub.1 hybrid progeny. If no restorer
gene is present in the male parent, male-sterile hybrids are
obtained. Such hybrids are useful where the vegetative tissue of
the corn plant is utilized, e.g., for silage, but in most cases,
the seeds will be deemed the most valuable portion of the crop, so
fertility of the hybrids in these crops must be restored.
Therefore, one aspect of the current invention concerns the hybrid
corn plant CH244084 comprising a genetic locus capable of restoring
male fertility in an otherwise male-sterile plant. Examples of
male-sterility genes and corresponding restorers which could be
employed with the plants of the invention are well known to those
of skill in the art of plant breeding and are disclosed in, for
instance, U.S. Pat. No. 5,530,191; U.S. Pat. No. 5,689,041; U.S.
Pat. No. 5,741,684; and U.S. Pat. No. 5,684,242, the disclosures of
which are each specifically incorporated herein by reference in
their entirety.
B. Herbicide Resistance
Numerous herbicide resistance genes are known and may be employed
with the invention. An example is a gene conferring resistance to a
herbicide that inhibits the growing point or meristem, such as an
imidazalinone or a sulfonylurea. Exemplary genes in this category
code for mutant ALS and AHAS enzyme as described, for example, by
Lee et al., (1988); Gleen et al., (1992); and Miki et al.,
(1990).
Resistance genes for glyphosate (resistance conferred by mutant
5-enolpyruvl-3 phosphikimate synthase (EPSP) and aroA genes,
respectively) and other phosphono compounds such as glufosinate
(phosphinothricin acetyl transferase (PAT) and Streptomyces
hygroscopicus phosphinothricin-acetyl transferase (bar) genes) may
also be used. See, for example, U.S. Pat. No. 4,940,835 to Shah, et
al., which discloses the nucleotide sequence of a form of EPSPS
which can confer glyphosate resistance. A DNA molecule encoding a
mutant aroA gene can be obtained under ATCC accession number 39256,
and the nucleotide sequence of the mutant gene is disclosed in U.S.
Pat. No. 4,769,061 to Comai. European patent application No. 0 333
033 to Kumada et al., and U.S. Pat. No. 4,975,374 to Goodman et
al., disclose nucleotide sequences of glutamine synthetase genes
which confer resistance to herbicides such as L-phosphinothricin.
The nucleotide sequence of a phosphinothricin-acetyltransferase
gene is provided in European application No. 0 242 246 to Leemans
et al. DeGreef et al., (1989), describe the production of
transgenic plants that express chimeric bar genes coding for
phosphinothricin acetyl transferase activity. Exemplary of genes
conferring resistance to phenoxy propionic acids and cycloshexones,
such as sethoxydim and haloxyfop are the Acct-S1, Accl-S2 and
Acct-S3 genes described by Marshall et al., (1992).
Genes are also known conferring resistance to a herbicide that
inhibits photosynthesis, such as a triazine (psbA and gs+ genes)
and a benzonitrile (nitrilase gene). Przibilla et al., (1991),
describe the transformation of Chlamydomonas with plasmids encoding
mutant psbA genes. Nucleotide sequences for nitrilase genes are
disclosed in U.S. Pat. No. 4,810,648 to Stalker, and DNA molecules
containing these genes are available under ATCC Accession Nos.
53435, 67441, and 67442. Cloning and expression of DNA coding for a
glutathione S-transferase is described by Hayes et al., (1992).
C. Waxy Starch
The waxy characteristic is an example of a recessive trait. In this
example, the progeny resulting from the first backcross generation
(BC1) must be grown and selfed. A test is then run on the selfed
seed from the BC1 plant to determine which BC1 plants carried the
recessive gene for the waxy trait. In other recessive traits
additional progeny testing, for example growing additional
generations such as the BC1S1, may be required to determine which
plants carry the recessive gene.
D. Disease Resistance
Plant defenses are often activated by specific interaction between
the product of a disease resistance gene (R) in the plant and the
product of a corresponding avirulence (Avr) gene in the pathogen. A
plant line can be transformed with cloned resistance gene to
engineer plants that are resistant to specific pathogen strains.
See, for example Jones et al., (1994) (cloning of the tomato Cf-9
gene for resistance to Cladosporium fulvum); Martin et al., (1993)
(tomato Pto gene for resistance to Pseudomonas syringae pv.
tomato); and Mindrinos et al., (1994) (Arabidopsis RPS2 gene for
resistance to Pseudomonas syringae).
A viral-invasive protein or a complex toxin derived therefrom may
also be used for viral disease resistance. For example, the
accumulation of viral coat proteins in transformed plant cells
imparts resistance to viral infection and/or disease development
effected by the virus from which the coat protein gene is derived,
as well as by related viruses. See Beachy et al., (1990). Coat
protein-mediated resistance has been conferred upon transformed
plants against alfalfa mosaic virus, cucumber mosaic virus, tobacco
streak virus, potato virus X, potato virus Y, tobacco etch virus,
tobacco rattle virus and tobacco mosaic virus. Id.
A virus-specific antibody may also be used. See, for example,
Tavladoraki et al., (1993), who show that transgenic plants
expressing recombinant antibody genes are protected from virus
attack.
Logemann et al., (1992), for example, disclose transgenic plants
expressing a barley ribosome-inactivating gene have an increased
resistance to fungal disease.
E. Insect Resistance
One example of an insect resistance gene includes a Bacillus
thuringiensis protein, a derivative thereof or a synthetic
polypeptide modeled thereon. See, for example, Geiser et al.,
(1986), who disclose the cloning and nucleotide sequence of a Bt
.delta.-endotoxin gene. Moreover, DNA molecules encoding
.delta.-endotoxin genes can be purchased from the American Type
Culture Collection, Manassas, Va., for example, under ATCC
Accession Nos. 40098, 67136, 31995 and 31998. Another example is a
lectin. See, for example, Van Damme et al., (1994), who disclose
the nucleotide sequences of several Clivia miniata mannose-binding
lectin genes. A vitamin-binding protein may also be used, such as
avidin. See PCT application US93/06487, the contents of which are
hereby incorporated by reference. This application teaches the use
of avidin and avidin homologues as larvicides against insect
pests.
Yet another insect resistance gene is an enzyme inhibitor, for
example, a protease or proteinase inhibitor or an amylase
inhibitor. See, for example, Abe et al., (1987) (nucleotide
sequence of rice cysteine proteinase inhibitor), Huub et al.,
(1993) (nucleotide sequence of cDNA encoding tobacco proteinase
inhibitor I), and Sumitani et al., (1993) (nucleotide sequence of
Streptomyces nitrosporeus .alpha.-amylase inhibitor). An
insect-specific hormone or pheromone may also be used. See, for
example, the disclosure by Hammock et al., (1990), of baculovirus
expression of cloned juvenile hormone esterase, an inactivator of
juvenile hormone.
Still other examples include an insect-specific antibody or an
immunotoxin derived therefrom and a developmental-arrestive
protein. See Taylor et al., (1994), who described enzymatic
inactivation in transgenic tobacco via production of single-chain
antibody fragments.
F. Modified Fatty Acid, Phytate and Carbohydrate Metabolism
Genes may be used conferring modified fatty acid metabolism. For
example, stearyl-ACP desaturase genes may be used. See Knutzon et
al., (1992). Various fatty acid desaturases have also been
described, such as a Saccharomyces cerevisiae OLE1 gene encoding
.DELTA.9 fatty acid desaturase, an enzyme which forms the
monounsaturated palmitoleic (16:1) and oleic (18:1) fatty acids
from palmitoyl (16:0) or stearoyl (18:0) CoA (McDonough et al.,
1992); a gene encoding a stearoyl-acyl carrier protein delta-9
desaturase from castor (Fox et al. 1993); .DELTA.6- and
.DELTA.12-desaturases from the cyanobacteria Synechocystis
responsible for the conversion of linoleic acid (18:2) to
gamma-linolenic acid (18:3 gamma) (Reddy et al. 1993); a gene from
Arabidopsis thaliana that encodes an omega-3 desaturase (Arondel et
al. 1992)); plant .DELTA.9-desaturases (PCT Application Publ. No.
WO 91/13972) and soybean and Brassica .DELTA.15 desaturases
(European Patent Application Publ. No. EP 0616644).
Phytate metabolism may also be modified by introduction of a
phytase-encoding gene to enhance breakdown of phytate, adding more
free phosphate to the transformed plant. For example, see Van
Hartingsveldt et al., (1993), for a disclosure of the nucleotide
sequence of an Aspergillus niger phytase gene. In corn, this, for
example, could be accomplished by cloning and then reintroducing
DNA associated with the single allele which is responsible for corn
mutants characterized by low levels of phytic acid. See Raboy et
al., (1990).
A number of genes are known that may be used to alter carbohydrate
metabolism. For example, plants may be transformed with a gene
coding for an enzyme that alters the branching pattern of starch.
See Shiroza et al., (1988) (nucleotide sequence of Streptococcus
mutans fructosyltransferase gene), Steinmetz et al., (1985)
(nucleotide sequence of Bacillus subtilis levansucrase gene), Pen
et al., (1992) (production of transgenic plants that express
Bacillus licheniformis .alpha.-amylase), Elliot et al., (1993)
(nucleotide sequences of tomato invertase genes), Sergaard et al.,
(1993) (site-directed mutagenesis of barley .alpha.-amylase gene),
and Fisher et al., (1993) (maize endosperm starch branching enzyme
II). The Z10 gene encoding a 10 kD zein storage protein from maize
may also be used to alter the quantities of 10 kD zein in the cells
relative to other components (Kirihara et al., 1988).
G. Origin and Breeding History of an Exemplary Introduced Trait
Provided by the invention are hybrid plant in which one or more of
the parents comprise an introduced trait. Such a plant may be
defined as comprising a single locus conversion. Exemplary
procedures for the preparation of such single locus conversions are
disclosed in U.S. Pat. No. 7,205,460, the entire disclosure of
which is specifically incorporated herein by reference.
An example of a single locus conversion is 85DGD1. 85DGD1 MLms is a
conversion of 85DGD1 to cytoplasmic male sterility. 85DGD1 MLms was
derived using backcross methods. 85DGD1 (a proprietary inbred of
Monsanto Company) was used as the recurrent parent and MLms, a
germplasm source carrying ML cytoplasmic sterility, was used as the
nonrecurrent parent. The breeding history of the converted inbred
85DGD1 MLms can be summarized as follows:
TABLE-US-00004 Hawaii Nurseries Planting Made up S-O: Female row
585 male Date Apr. 02, 1992 row 500 Hawaii Nurseries Planting S-O
was grown and plants were Date Jul. 15, 1992 backcrossed times
85DGD1 (rows 444 {acute over ( )} 443) Hawaii Nurseries Planting
Bulked seed of the BC1 was grown and Date Nov. 18, 1992 backcrossed
times 85DGD1 (rows V3-27 {acute over ( )} V3-26) Hawaii Nurseries
Planting Bulked seed of the BC2 was grown and Date Apr. 02, 1993
backcrossed times 85DGD1 (rows 37 {acute over ( )} 36) Hawaii
Nurseries Planting Bulked seed of the BC3 was grown and Date Jul.
14, 1993 backcrossed times 85DGD1 (rows 99 {acute over ( )} 98)
Hawaii Nurseries Planting Bulked seed of BC4 was grown and Date
Oct. 28, 1993 backcrossed times 85DGD1 (rows KS-63 {acute over ( )}
KS-62) Summer 1994 A single ear of the BC5 was grown and
backcrossed times 85DGD1 (MC94-822 {acute over ( )} MC94-822-7)
Winter 1994 Bulked seed of the BC6 was grown and backcrossed times
85DGD1 (3Q-1 {acute over ( )} 3Q-2) Summer 1995 Seed of the BC7 was
bulked and named 85DGD1 MLms.
As described, techniques for the production of corn plants with
added traits are well known in the art (see, e.g., Poehlman et al.,
1995; Fehr, 1987; Sprague and Dudley, 1988). A non-limiting example
of such a procedure one of skill in the art could use for
preparation of a hybrid corn plant CH244084 comprising an added
trait is as follows: (a) crossing a parent of hybrid corn plant
CH244084 such as CV721680 and/or I226218 to a second (nonrecurrent)
corn plant comprising a locus to be converted in the parent; (b)
selecting at least a first progeny plant resulting from the
crossing and comprising the locus; (c) crossing the selected
progeny to the parent line of corn plant CH244084; (d) repeating
steps (b) and (c) until a parent line of variety CH244084 is
obtained comprising the locus; and (e) crossing the converted
parent with the second parent to produce hybrid variety CH244084
comprising a desired trait.
Following these steps, essentially any locus may be introduced into
hybrid corn variety CH244084. For example, molecular techniques
allow introduction of any given locus, without the need for
phenotypic screening of progeny during the backcrossing steps.
PCR and Southern hybridization are two examples of molecular
techniques that may be used for confirmation of the presence of a
given locus and thus conversion of that locus. The techniques are
carried out as follows: Seeds of progeny plants are grown and DNA
isolated from leaf tissue (see Sambrook et al., 2001; Shure et al.
1983). Approximately one gram of leaf tissue is lyophilized
overnight in 15 ml polypropylene tubes. Freeze-dried tissue is
ground to a powder in the tube using a glass rod. Powdered tissue
is mixed thoroughly with 3 ml extraction buffer (7.0 urea, 0.35 M
NaCl, 0.05 M Tris-HCl pH 8.0, 0.01 M EDTA, 1% sarcosine).
Tissue/buffer homogenate is extracted with 3 ml phenol/chloroform.
The aqueous phase is separated by centrifugation, and precipitated
twice using 1/10 volume of 4.4 M ammonium acetate pH 5.2, and an
equal volume of isopropanol. The precipitate is washed with 75%
ethanol and resuspended in 100-500 .mu.l TE (0.01 M Tris-HCl, 0.001
M EDTA, pH 8.0). The DNA may then be screened as desired for
presence of the locus.
For PCR, two hundred to 1000 ng genomic DNA from the progeny plant
being screened is added to a reaction mix containing 10 mM Tris-HCl
pH 8.3, 1.5 mM MgCl.sub.2, 50 mM KCl, 0.1 mg/ml gelatin, 200 .mu.M
each dATP, dCTP, dGTP, dTTP, 20% glycerol, 2.5 units Taq DNA
polymerase and 0.5 .mu.M each of forward and reverse DNA primers
that span a segment of the locus being converted. The reaction is
run in a thermal cycling machine 3 minutes at 94 C, 39 repeats of
the cycle 1 minute at 94 C, 1 minute at 50 C, 30 seconds at 72 C,
followed by 5 minutes at 72 C. Twenty .mu.l of each reaction mix is
run on a 3.5% NuSieve gel in TBE buffer (90 mM Tris-borate, 2 mM
EDTA) at 50V for two to four hours. The amplified fragment is
detected using an agarose gel. Detection of an amplified fragment
corresponding to the segment of the locus spanned by the primers
indicates the presence of the locus.
For Southern analysis, plant DNA is restricted, separated in an
agarose gel and transferred to a Nylon filter in 10.times.SCP (20
SCP: 2M NaCl, 0.6 M disodium phosphate, 0.02 M disodium EDTA)
according to standard methods (Southern, 1975). Locus DNA or RNA
sequences are labeled, for example, radioactively with .sup.32P by
random priming (Feinberg & Vogelstein, 1983). Filters are
prehybridized in 6.times.SCP, 10% dextran sulfate, 2% sarcosine,
and 500 .mu.g/ml denatured salmon sperm DNA. The labeled probe is
denatured, hybridized to the filter and washed in 2.times.SCP, 1%
SDS at 65.degree. for 30 minutes and visualized by autoradiography
using Kodak XAR5 film. Presence of the locus is indicated by
detection of restriction fragments of the appropriate size.
VI. Tissue Cultures and in Vitro Regeneration of Corn Plants
A further aspect of the invention relates to tissue cultures of the
corn plant designated CH244084. As used herein, the term "tissue
culture" indicates a composition comprising isolated cells of the
same or a different type or a collection of such cells organized
into parts of a plant. Exemplary types of tissue cultures are
protoplasts, calli and plant cells that are intact in plants or
parts of plants, such as embryos, pollen, flowers, kernels, ears,
cobs, leaves, husks, stalks, roots, root tips, anthers, silk, and
the like. In a preferred embodiment, the tissue culture comprises
embryos, protoplasts, meristematic cells, pollen, leaves or anthers
derived from immature tissues of these plant parts. Means for
preparing and maintaining plant tissue cultures are well known in
the art (U.S. Pat. No. 5,538,880; and U.S. Pat. No. 5,550,318, each
incorporated herein by reference in their entirety). By way of
example, a tissue culture comprising organs such as tassels or
anthers has been used to produce regenerated plants (U.S. Pat. No.
5,445,961 and U.S. Pat. No. 5,322,789; the disclosures of which are
incorporated herein by reference).
One type of tissue culture is tassel/anther culture. Tassels
contain anthers which in turn enclose microspores. Microspores
develop into pollen. For anther/microspore culture, if tassels are
the plant composition, they are preferably selected at a stage when
the microspores are uninucleate, that is, include only one, rather
than 2 or 3 nuclei. Methods to determine the correct stage are well
known to those skilled in the art and include mitramycin
fluorescent staining (Pace et al., 1987), trypan blue (preferred)
and acetocarmine squashing. The mid-uninucleate microspore stage
has been found to be the developmental stage most responsive to the
subsequent methods disclosed to ultimately produce plants.
Although microspore-containing plant organs such as tassels can
generally be pretreated at any cold temperature below about
25.degree. C., a range of 4 to 25.degree. C. is preferred, and a
range of 8 to 14.degree. C. is particularly preferred. Although
other temperatures yield embryoids and regenerated plants, cold
temperatures produce optimum response rates compared to
pretreatment at temperatures outside the preferred range. Response
rate is measured as either the number of embryoids or the number of
regenerated plants per number of microspores initiated in culture.
Exemplary methods of microspore culture are disclosed in, for
example, U.S. Pat. No. 5,322,789 and U.S. Pat. No. 5,445,961, the
disclosures of which are specifically incorporated herein by
reference.
Although not required, when tassels are employed as the plant
organ, it is generally preferred to sterilize their surface.
Following surface sterilization of the tassels, for example, with a
solution of calcium hypochloride, the anthers are removed from
about 70 to 150 spikelets (small portions of the tassels) and
placed in a preculture or pretreatment medium. Larger or smaller
amounts can be used depending on the number of anthers.
When one elects to employ tassels directly, tassels are preferably
pretreated at a cold temperature for a predefined time, preferably
at 10.degree. C. for about 4 days. After pretreatment of a whole
tassel at a cold temperature, dissected anthers are further
pretreated in an environment that diverts microspores from their
developmental pathway. The function of the preculture medium is to
switch the developmental program from one of pollen development to
that of embryoid/callus development. An embodiment of such an
environment in the form of a preculture medium includes a sugar
alcohol, for example mannitol or sorbitol, inositol or the like. An
exemplary synergistic combination is the use of mannitol at a
temperature of about 10.degree. C. for a period ranging from about
10 to 14 days. In a preferred embodiment, 3 ml of 0.3 M mannitol
combined with 50 mg/l of ascorbic acid, silver nitrate, and
colchicine is used for incubation of anthers at 10.degree. C. for
between 10 and 14 days. Another embodiment is to substitute
sorbitol for mannitol. The colchicine produces chromosome doubling
at this early stage. The chromosome doubling agent is preferably
only present at the preculture stage.
It is believed that the mannitol or other similar carbon structure
or environmental stress induces starvation and functions to force
microspores to focus their energies on entering developmental
stages. The cells are unable to use, for example, mannitol as a
carbon source at this stage. It is believed that these treatments
confuse the cells causing them to develop as embryoids and plants
from microspores. Dramatic increases in development from these
haploid cells, as high as 25 embryoids in 10.sup.4 microspores,
have resulted from using these methods.
To isolate microspores, an isolation media is preferred. An
isolation media is used to separate microspores from the anther
walls while maintaining their viability and embryogenic potential.
An illustrative embodiment of an isolation media includes a 6%
sucrose or maltose solution combined with an antioxidant such as 50
mg/l of ascorbic acid, 0.1 mg/l biotin, and 400 mg/l of proline,
combined with 10 mg/l of nicotinic acid and 0.5 mg/l AgNO.sub.3. In
another embodiment, the biotin and proline are omitted.
An isolation media preferably has a higher antioxidant level where
it is used to isolate microspores from a donor plant (a plant from
which a plant composition containing a microspore is obtained) that
is field grown in contrast to greenhouse grown. A preferred level
of ascorbic acid in an isolation medium is from about 50 mg/l to
about 125 mg/l and, more preferably, from about 50 mg/l to about
100 mg/l.
One can find particular benefit in employing a support for the
microspores during culturing and subculturing. Any support that
maintains the cells near the surface can be used. An illustrative
embodiment of a solid support is a TRANSWELL.RTM. culture dish.
Another embodiment of a solid support for development of the
microspores is a bilayer plate wherein liquid media is on top of a
solid base. Other embodiments include a mesh or a millipore filter.
Preferably, a solid support is a nylon mesh in the shape of a raft.
A raft is defined as an approximately circular support material
which is capable of floating slightly above the bottom of a tissue
culture vessel, for example, a petri dish, of about a 60 or 100 mm
size, although any other laboratory tissue culture vessel will
suffice. In an illustrative embodiment, a raft is about 55 mm in
diameter.
Culturing isolated microspores on a solid support, for example, on
a 10 mm pore nylon raft floating on 2.2 ml of medium in a 60 mm
petri dish, prevents microspores from sinking into the liquid
medium and thus avoiding low oxygen tension. These types of cell
supports enable the serial transfer of the nylon raft with its
associated microspore/embryoids ultimately to full strength medium
containing activated charcoal and solidified with, for example,
GELRITE.TM. (solidifying agent).
The liquid medium passes through the mesh while the microspores are
retained and supported at the medium-air interface. The surface
tension of the liquid medium in the petri dish causes the raft to
float. The liquid is able to pass through the mesh; consequently,
the microspores stay on top. The mesh remains on top of the total
volume of liquid medium.
The culture vessels can be further defined as either (1) a bilayer
60 mm petri plate wherein the bottom 2 ml of medium are solidified
with 0.7% agarose overlaid with 1 mm of liquid containing the
microspores; (2) a nylon mesh raft wherein a wafer of nylon is
floated on 1.2 ml of medium and 1 ml of isolated microspores is
pipetted on top; or (3) TRANSWELL.RTM. plates wherein isolated
microspores are pipetted onto membrane inserts which support the
microspores at the surface of 2 ml of medium.
Examples of processes of tissue culturing and regeneration of corn
are described in, for example, European Patent Application 0 160
390, Green and Rhodes (1982) and Duncan et al. (1985), Songstad et
al. (1988), Rao et al. (1986), Conger et al. (1987), PCT
Application WO 95/06128, Armstrong and Green, 1985; Gordon-Kamm et
al., 1990, and U.S. Pat. No. 5,736,369.
VII. Processes of Preparing Corn Plants and the Corn Plants
Produced by Such Crosses
The present invention provides processes of preparing novel corn
plants and corn plants produced by such processes. In accordance
with such a process, a first parent corn plant may be crossed with
a second parent corn plant wherein the first and second corn plants
are the parent lines of hybrid corn plant variety CH244084, or
wherein at least one of the plants is of hybrid corn plant variety
CH244084.
Corn plants (Zea mays L.) can be crossed by either natural or
mechanical techniques. Natural pollination occurs in corn when wind
blows pollen from the tassels to the silks that protrude from the
tops of the recipient ears. Mechanical pollination can be effected
either by controlling the types of pollen that can blow onto the
silks or by pollinating by hand. In one embodiment, crossing
comprises the steps of: (a) planting in pollinating proximity seeds
of a first and a second parent corn plant, and preferably, seeds of
a first inbred corn plant and a second, distinct inbred corn plant;
(b) cultivating or growing the seeds of the first and second parent
corn plants into plants that bear flowers; (c) emasculating flowers
of either the first or second parent corn plant, i.e., treating the
flowers so as to prevent pollen production, or alternatively, using
as the female parent a male sterile plant, thereby providing an
emasculated parent corn plant; (d) allowing natural
cross-pollination to occur between the first and second parent corn
plants; (e) harvesting seeds produced on the emasculated parent
corn plant; and, where desired, (f) growing the harvested seed into
a corn plant, preferably, a hybrid corn plant.
Parental plants are typically planted in pollinating proximity to
each other by planting the parental plants in alternating rows, in
blocks or in any other convenient planting pattern. Where the
parental plants differ in timing of sexual maturity, it may be
desired to plant the slower maturing plant first, thereby ensuring
the availability of pollen from the male parent during the time at
which silks on the female parent are receptive to pollen. Plants of
both parental parents are cultivated and allowed to grow until the
time of flowering. Advantageously, during this growth stage, plants
are in general treated with fertilizer and/or other agricultural
chemicals as considered appropriate by the grower.
At the time of flowering, in the event that plant CH244084 is
employed as the male parent, the tassels of the other parental
plant are removed from all plants employed as the female parental
plant to avoid self-pollination. The detasseling can be achieved
manually but also can be done by machine, if desired.
Alternatively, when the female parent corn plant comprises a
cytoplasmic or nuclear gene conferring male sterility, detasseling
may not be required. Additionally, a chemical gametocide may be
used to sterilize the male flowers of the female plant. In this
case, the parent plants used as the male may either not be treated
with the chemical agent or may comprise a genetic factor which
causes resistance to the emasculating effects of the chemical
agent. Gametocides affect processes or cells involved in the
development, maturation or release of pollen. Plants treated with
such gametocides are rendered male sterile, but typically remain
female fertile. The use of chemical gametocides is described, for
example, in U.S. Pat. No. 4,936,904, the disclosure of which is
specifically incorporated herein by reference in its entirety.
Furthermore, the use of Roundup herbicide in combination with
glyphosate tolerant corn plants to produce male sterile corn plants
is disclosed in PCT Publication WO 98/44140.
Following emasculation, the plants are then typically allowed to
continue to grow and natural cross-pollination occurs as a result
of the action of wind, which is normal in the pollination of
grasses, including corn. As a result of the emasculation of the
female parent plant, all the pollen from the male parent plant is
available for pollination because tassels, and thereby pollen
bearing flowering parts, have been previously removed from all
plants of the plant being used as the female in the hybridization.
Of course, during this hybridization procedure, the parental
varieties are grown such that they are isolated from other corn
fields to minimize or prevent any accidental contamination of
pollen from foreign sources. These isolation techniques are well
within the skill of those skilled in this art.
Both parental plants of corn may be allowed to continue to grow
until maturity or the male rows may be destroyed after flowering is
complete. Only the ears from the female parental plants are
harvested to obtain seeds of a novel F.sub.1 hybrid. The novel
F.sub.1 hybrid seed produced can then be planted in a subsequent
growing season in commercial fields or, alternatively, advanced in
breeding protocols for purposes of developing novel inbred
lines.
Alternatively, in another embodiment of the invention, one or both
first and second parent corn plants can be from variety CH244084.
Thus, any corn plant produced using corn plant CH244084 forms a
part of the invention. As used herein, crossing can mean selfing,
backcrossing, crossing to another or the same variety, crossing to
populations, and the like. All corn plants produced using the corn
variety CH244084 as a parent are, therefore, within the scope of
this invention.
One use of the instant corn variety is in the production of hybrid
seed. Any time the corn plant CH244084 is crossed with another,
different, corn plant, a corn hybrid plant is produced. As such,
hybrid corn plant can be produced by crossing CH244084 with any
second corn plant. Essentially any other corn plant can be used to
produce a corn plant having corn plant CH244084 as one parent. All
that is required is that the second plant be fertile, which corn
plants naturally are, and that the plant is not corn variety
CH244084.
The goal of the process of producing an F.sub.1 hybrid is to
manipulate the genetic complement of corn to generate new
combinations of genes which interact to yield new or improved
traits (phenotypic characteristics). A process of producing an
F.sub.1 hybrid typically begins with the production of one or more
inbred plants. Those plants are produced by repeated crossing of
ancestrally related corn plants to try to combine certain genes
within the inbred plants.
Corn has a diploid phase which means two conditions of a gene (two
alleles) occupy each locus (position on a chromosome). If the
alleles are the same at a locus, there is said to be homozygosity.
If they are different, there is said to be heterozygosity. In a
completely inbred plant, all loci are homozygous. Because many loci
when homozygous are deleterious to the plant, in particular leading
to reduced vigor, less kernels, weak and/or poor growth, production
of inbred plants is an unpredictable and arduous process. Under
some conditions, heterozygous advantage at some loci effectively
bars perpetuation of homozygosity.
A single cross hybrid corn variety is the cross of two inbred
plants, each of which has a genotype which complements the genotype
of the other. Typically, F.sub.1 hybrids are more vigorous than
their inbred parents. This hybrid vigor, or heterosis, is
manifested in many polygenic traits, including markedly improved
yields, better stalks, better roots, better uniformity and better
insect and disease resistance. In the development of hybrids only
the F.sub.1 hybrid plants are typically sought. An F.sub.1 single
cross hybrid is produced when two inbred plants are crossed. A
double cross hybrid is produced from four inbred plants crossed in
pairs (A.times.B and C.times.D) and then the two F1 hybrids are
crossed again (A.times.B).times.(C.times.D).
Thousands of corn varieties are known to those of skill in the art,
any one of which could be crossed with corn plant CH244084 to
produce a hybrid plant. For example, the U.S. Patent &
Trademark Office has issued more than 300 utility patents for corn
varieties. Estimates place the number of different corn accessions
in genebanks around the world at around 50,000 (Chang, 1992). The
Maize Genetics Cooperation Stock Center, which is supported by the
U.S. Department of Agriculture, has a total collection approaching
80,000 individually pedigreed samples
(//w3.ag.uiuc.edu/maize-coop/mgc-info.html).
When the corn plant CH244084 is crossed with another plant to yield
progeny, it can serve as either the maternal or paternal plant. For
many crosses, the outcome is the same regardless of the assigned
sex of the parental plants. However, due to increased seed yield
and production characteristics, it may be desired to use one
parental plant as the maternal plant. Some plants produce tighter
ear husks leading to more loss, for example due to rot. There can
be delays in silk formation which deleteriously affect timing of
the reproductive cycle for a pair of parental inbreds. Seed coat
characteristics can be preferable in one plant. Pollen can be shed
better by one plant. Other variables can also affect preferred
sexual assignment of a particular cross.
The development of a hybrid corn variety involves three steps: (1)
the selection of plants from various germplasm pools; (2) the
selfing of the selected plants for several generations to produce a
series of inbred plants, which, although different from each other,
each breed true and are highly uniform; and (3) crossing the
selected inbred plants with unrelated inbred plants to produce the
hybrid progeny (F.sub.1). During the inbreeding process in corn,
the vigor of the plants decreases. Vigor is restored when two
unrelated inbred plants are crossed to produce the hybrid progeny
(F.sub.1). An important consequence of the homozygosity and
homogeneity of the inbred plants is that the hybrid between any two
inbreds is always the same. Once the inbreds that give a superior
hybrid have been identified, hybrid seed can be reproduced
indefinitely as long as the homogeneity of the inbred parents is
maintained. Conversely, much of the hybrid vigor exhibited by
F.sub.1 hybrids is lost in the next generation (F.sub.2).
Consequently, seed from hybrid varieties is not used for planting
stock. It is not generally beneficial for farmers to save seed of
F.sub.1 hybrids. Rather, farmers purchase F.sub.1 hybrid seed for
planting every year.
The development of inbred plants generally requires at least about
5 to 7 generations of selfing. Inbred plants are then cross-bred in
an attempt to develop improved F.sub.1 hybrids. Hybrids are then
screened and evaluated in small scale field trials. Typically,
about 10 to 15 phenotypic traits, selected for their potential
commercial value, are measured. A selection index of the most
commercially important traits is used to help evaluate hybrids.
FACT, an acronym for Field Analysis Comparison Trial (strip
trials), is an on-farm experimental testing program employed by
Monsanto Company to perform the final evaluation of the commercial
potential of a product.
During the next several years, a progressive elimination of hybrids
occurs based on more detailed evaluation of their phenotype.
Eventually, strip trials (FACT) are conducted to formally compare
the experimental hybrids being developed with other hybrids, some
of which were previously developed and generally are commercially
successful. That is, comparisons of experimental hybrids are made
to competitive hybrids to determine if there was any advantage to
further development of the experimental hybrids. Examples of such
comparisons are presented herein. After FACT testing is complete,
determinations may be made whether commercial development should
proceed for a given hybrid.
The present invention provides a genetic complement of the hybrid
corn plant variety designated CH244084. As used herein, the phrase
"genetic complement" means an aggregate of nucleotide sequences,
the expression of which defines the phenotype of a corn plant or a
cell or tissue of that plant. By way of example, a corn plant is
genotyped to determine a representative sample of the inherited
markers it possesses. Markers are alleles at a single locus. They
are preferably inherited in codominant fashion so that the presence
of both alleles at a diploid locus is readily detectable, and they
are free of environmental variation, i.e., their heritability is 1.
This genotyping is preferably performed on at least one generation
of the descendant plant for which the numerical value of the
quantitative trait or traits of interest are also determined. The
array of single locus genotypes is expressed as a profile of marker
alleles, two at each locus. The marker allelic composition of each
locus can be either homozygous or heterozygous. Homozygosity is a
condition where both alleles at a locus are characterized by the
same nucleotide sequence or size of a repeated sequence.
Heterozygosity refers to different conditions of the gene at a
locus. A preferred type of genetic marker for use with the
invention is simple sequence repeats (SSRs), although potentially
any other type of genetic marker could be used, for example,
restriction fragment length polymorphisms (RFLPs), amplified
fragment length polymorphisms (AFLPs), single nucleotide
polymorphisms (SNPs), and isozymes.
All of the compositions and methods disclosed and claimed herein
can be made and executed without undue experimentation in light of
the present disclosure. While the compositions and methods of this
invention have been described in terms of the foregoing
illustrative embodiments, it will be apparent to those of skill in
the art that variations, changes, modifications, and alterations
may be applied to the composition, methods, and in the steps or in
the sequence of steps of the methods described herein, without
departing from the true concept, spirit, and scope of the
invention. More specifically, it will be apparent that certain
agents that are both chemically and physiologically related may be
substituted for the agents described herein while the same or
similar results would be achieved. All such similar substitutes and
modifications apparent to those skilled in the art are deemed to be
within the spirit, scope, and concept of the invention as defined
by the appended claims.
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